Separating an antithrombotic effect from an antihemostatic effect. (A) Ferric chloride–induced carotid artery occlusion model. The carotid artery is briefly exposed to a pad saturated with FeCl₃, and blood flow through the vessel is monitored for 30 minutes. Each bar represents a group of 10 mice, and the bar height indicates the percent of each group with patent blood vessels at the end of the experiment. Note that all wild-type mice (red bars) have occluded arteries with 3.5% FeCl₃, whereas mice treated with heparin (blue bars), or mice deficient in FIX (orange bars) or FXI (green bars) require higher concentrations of FeCl₃ to induce vessel occlusion. (B) Tail bleeding times. Wild-type mice treated with vehicle (red bar) or heparin (blue bar), or mice lacking FIX (orange bar), or FXI (green bar) underwent removal of the tail tip. The bleeding tail was immersed in normal saline at 37°C, and time to cessation of bleeding was recorded. Results are the mean bleeding times for groups of 10 mice ± 1 standard deviation. If bleeding did not stop by the 2000-second time point, the tail was cauterized.